1. Field of the Invention
The present invention relates to data storage devices, and more particularly, the present invention relates to the positional control of a magnetic head relative to a data storage medium.
A claim of priority under 35 U.S.C. § 119 is made to Korean Patent Application No. 2006-0065297, filed Jul. 12, 2006, the disclosure of which is hereby incorporated by reference herein as if set forth in its entirety.
2. Description of the Related Art
Data storage devices, such as hard disk drives, are used as auxiliary memory for computer systems, and typically include a data storage medium (e.g., a disk) which stores data and a magnetic head. The magnetic head includes a write head (or write element) used to write data into the data storage medium and a read head (or read element) used to read data from the data storage medium.
Together with increases in tracks per inch (TPI) and bits per inch (BPI), the amount of data stored in a data storage medium has rapidly increased and the size of the data storage medium has rapidly decreased. As such, it has become necessary to decrease the floating height or flying height (FH) of a magnetic head from a surface of the data storage medium in order to increase the write performance of a write head and/or the read performance of a read head. Generally, the distance between a magnetic head and a data storage medium is referred to as a floating height, a flying height, a clearance, a head gap, a spacing or a spacing loss.
However, when the FH of a magnetic head decreases, the magnetic head can easily collide with the surface of the data storage medium when subjected to even minor impact during operation, and therefore, the magnetic head and/or the surface of the data storage medium may be damaged. Accordingly, it is necessary to appropriately control the FH.
There have been attempts to maximize the capacity of a data storage device by appropriately controlling the FH, and flying-on-demand (FOD) is an example of one such attempt. FOD is a method of controlling the FH using thermal expansion of a pole tip hat located at an end of a magnetic head.
FOD may be implemented using a slider having an air bearing surface (ABS) (which is referred to as an “air bearing slider”). In detail, a heater similar to a write coil of a write head is provided on the ABS and current for FOD is supplied to the heater. Then, the end of the ABS expands due to heat and changes the FH. Accordingly, the FH can be adjusted by controlling the amount of current supplied to the heater.
Generally, the FH or clearance can be measured using a touchdown method while the current supplied to the heater is being controlled. In the touchdown method, a current FH of a magnetic head is a distance between the current FH and a height at which the magnetic head touches down on the surface of a storage medium (i.e., the FH is “0”). However, it is troublesome for users to measure the FH using the touchdown method every time. Moreover, any change in the FH caused by variations in temperature, humidity, or air pressure decreases the reliability of a data storage device.